Most nonelderly Americans purchase health insurance through
their employers, which sponsor a limited number of plans. Using
a panel dataset representing over ten million insured lives, we estimate employees' preferences for different health plans and use the
estimates to predict their choices if more plans were made available
to them on the same terms, i.e., with equivalent subsidies and at
large-group prices. Using conservative assumptions, we estimate a
median welfare gain of 13 percent of premiums. A proper accounting
of the costs and benefits of a transition from employer-sponsored
to individually-purchased insurance should include this nontrivial
gain. (JEL G22, I13, J32)